The invention relates to dairy harvesting facility milk pumps, and more particularly to electrically insulated milk pumps.
In dairy harvesting facilities, electrical equipment and structures must be electrically insulated from other equipment, operators and animals to minimize and/or avoid electrical shock, stray voltage and other problems. Insulating electrical equipment is sometimes difficult even in well designed and constructed dairies.
For example, stray voltage can occur with a grounded-neutral wiring system on a dairy harvesting facility. If stray voltage reaches sufficient levels, electric shocks can be transmitted to operators and animals when contacting grounded devices. A number of remedies can be used to reduce stray voltage, and installing an equipotential plane is one of them. An equipotential plane is an electrically conductive grid usually embedded in concrete and connected to the electrical grounding system. From a human safety standpoint the equipotential ground “cow ground” and the equipment ground “milk pump ground,” are tied together in a properly installed facility at the point where electricity enters the facility. This means in a normal installation (before a failure occurs) there should be no difference in potential (voltage) between the two.
Problems also arise in connections between conducting materials that significantly impede current flow and can place an equipotential plane at a high potential with respect to earth. High impedance connections between metallic members subject to large amounts of current due to power system faults can be extremely hazardous to personnel and equipment. Most types of equipment include suitable protection against current flowing from the electrical equipment to operators and dairy animals in event of ground or neutral failure in the equipment.
An exception to this appears to be in milk pumps used to transfer milk through various pipelines and treatment devices (such as pasteurizers) in dairy harvesting facilities. Milk pumps include an electric motor and a pump driven by the motor. Current milk pump designs do not protect animals from electrical shock if the electrical circuit to the motor fails due to incorrect wiring, worn insulation, mechanical damage, or voltage surges. It is possible for stray electrical current to pass from the motor frame to the metal components of the milk pump and the stainless steel milk lines used to carry milk from the cow to the milk collection receiver and the milk cooling tank. This has the potential to harm animals and operators who are in contact with these dairy system components.
Current installation guidelines require that animals and operators be protected from stray currents by installing equipotential planes connected to dairy milk lines. Nonetheless, milk pumps are mechanically driven by electric motors, so a potential stray current could pass to the milk line because of its connection to the equipotential plane.
Most dairy equipment is designed to impede current flow and meet the installation guidelines, but milk pumps have long been neglected as a source of electrical current despite the well known possibility of stray voltage and electric shock. Thus, there are needed apparatus and methods to electrically insulate milk pumps from operators, animals, and dairy facility equipment.